linux-kernel - Re: [BUG 2.6.36-rc6] list corruption in module_bug

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <201010041300.15234.arnd@arndb.de>
Date:	Mon, 4 Oct 2010 13:00:14 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Kay Sievers <kay.sievers@...y.org>,
	Brandon Philips <brandon@...p.org>
Subject: Re: [BUG 2.6.36-rc6] list corruption in module_bug_finalize

On Sunday 03 October 2010, Thomas Gleixner wrote:
> Current mainline triggers a list corruption bug in
> module_bug_finalize(). dmesg excerpt below.
> 
> The corresponding code says:
> 
>         /*
>          * Strictly speaking this should have a spinlock to protect against
>          * traversals, but since we only traverse on BUG()s, a spinlock
>          * could potentially lead to deadlock and thus be counter-productive.
>          */
>         list_add(&mod->bug_list, &module_bug_list);
> 
> I can see the traversal problem vs. BUG(), but what's protecting the
> list_add() ? BKL probably did, but is that true anymore ?

BKL hasn't been in this code path since before git.

I think this relatively recent change caused module_finalize to be
called without module_mutex held:

commit 75676500f8298f0ee89db12db97294883c4b768e
Author: Rusty Russell <rusty@...tcorp.com.au>
Date:   Sat Jun 5 11:17:36 2010 -0600

    module: make locking more fine-grained.
    
    Kay Sievers <kay.sievers@...y.org> reports that we still have some
    contention over module loading which is slowing boot.
    
    Linus also disliked a previous "drop lock and regrab" patch to fix the
    bne2 "gave up waiting for init of module libcrc32c" message.
    
    This is more ambitious: we only grab the lock where we need it.
    
    Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
    Cc: Brandon Philips <brandon@...p.org>
    Cc: Kay Sievers <kay.sievers@...y.org>
    Cc: Linus Torvalds <torvalds@...ux-foundation.org>

	Arnd
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/